1. Field of the Invention
The present invention relates to an ink feeding apparatus for feeding ink supplied from an ink tank through an ink path to an ink jet recording head, and in particular, relates to an ink feeding apparatus using a bellows pump as an ink feeding mechanism. The present invention also relates to an ink jet recording apparatus building in such an ink feeding apparatus.
2. Description of Related Art
Conventionally, an image recording apparatus of a so-called ink jet type has been known, that records images on a recording paper by allowing ink droplets to jet from a recording head and impact on the recording paper. In such an ink jet recording apparatus, a configuration in which ink is supplied to the recording head from an ink tank for storing ink through a predetermined ink path, is adopted.
In such conventional ink jet recording apparatus, however, there is a problem of bubbles generated in the ink path in an ink supply path. Bubbles are generated by various cause. For example, there may be such a case where gas dissolved in ink appears as bubbles due to change of temperature, or exterior air reaches the ink path by penetrating an ink tube or the like. In any case, bubbles generated in the ink path will lead to poor ink jetting from the recording head.
In a conventional ink jet recording apparatus as described above, an invention has been proposed, which makes possible to remove bubbles generated in the ink path together with ink by a sucking operation called purge or the like (See, for example, Japanese Patent Application Laid-Open No. H06-8473 (1996)). Also, a technology of removing bubbles in the ink path while jetting ink from the recording head by driving a pump provided in the ink path, has been proposed.
In the aforementioned conventional technology, a bellows pump has been known as a pump to be provided in the ink path. The bellows pump generates pumping pressure by deforming a bellows-shaped tubular body to expand and contract. Even in such a bellows pump, bubbles may be generated in ink resulting from change of temperature or the like. When bubbles should grow making such generated bubbles a core thereof, ink flows in the ink path may be blocked, or poor ink jetting may be caused by bubbles reaching the recording head. Therefore, in the bellows pump, it is desirable that bubbles are not generated, and even if bubbles are generated, it is desirable that they are removed before growing larger.